Electrode for measuring alternating voltages in an electrolyte

ABSTRACT

The invention relates to an electrode consisting of a conductor and adjacent to said conductor an electrolyt body, that contains copper ions. The electrolyt body is immobilized by a pervious structure, that may consist of a fine copper wire folded randomly in a recess containing the electrolyt body. Preferably the electrolyt body is bounded by a perforated plate.

Van Breugel 5] July 18, 1972 54] ELECTRODE FOR MEASURING 1,910,7095/1933 Mortenson ..204/19s R x ALTERNATING VOLTAGES IN AN 3,149,2539/1964 Luebke ..310/11 ELE LYTE 3,272,731 9/1966 Hutchison et a]..204/280 X CTRO 3,275,860 9/1966 Way ..310/1 1 [72] Inventor: JohannesG. A. Van Breugel, Amstellaan 3,354,644 11/1967 Moore, Jr ..3l0/11 UX20, Heemstede, Netherlands 3,416,013 12/1968 Poncelet et al. ..3 10/1 1Filed: y 22 1970 3,483,111 12/1969 Zaromb ..204/195 R 1 AppL 39,794Primary Examiner-Charles A. Ruehl Attomey--Brumbaugh, Graves, Donohue &Raymond [52] 11.8. CI. ..73/194 EM, 32402962232112, 57 ABSTRACT 51 1m.01. .5011 1/00, GOlp 5/08 The electmde misting 0f [58] Field of Search..73/194 EM; 204/280 283 284 and adjacent Said cnductr electmly 204/195310/1 tains copper ions. The electrolyt body is immobilized by apervious sh'ucture, that may consist of a fine copper wire folded 56 R fCit randomly in a recess containing the electrolyt body. 1 e erences edPreferably the electrolyt body is bounded by a perforated UNITED STATESPATENTS P 2,607,223 8/1952 Fleming ..73/194 EM 6 Claims, 1 DrawingFigure PATENTED JUL1B|972 3.577083 INVENTOR.

JOHANNES G. A. VAN BREUGEL ELECTRODE FOR MEASURING ALTERNATING VOLTAGESIN AN ELECIROLYTE When measuring voltages in a moving electrolyt, e.g.for measuring the flow velocity by means of measuring the voltage whichis generated between electrodes in a magnetic field, considerabledisturbances occur, which limit the exactness of the measurement.

So far electrodes of stainless steel have been suggested for measuringvoltage in seawater. These indeed have the ad vantage of hardly any orextremely small corrosion, but on the other hand they have considerabledisadvantages with respect to disturbances in the measurement, becausejuxta-positioned crystals have somewhat different compositions andbecause the interface potentials of the crystals are dependent on thecrystal orientation. Moreover it has appeared that acorn-shells and thelike can grow on the electrode, which can induce very importantdisturbances.

For measuring the flow velocity of an electrically conducting liquid inpipe lines silver electrodes have already been suggested.

The disturbances in the measurement mainly arise because ofinhomogeneities of the electrode which lead to different interfacepotentials and, owing thereto, to difierent current densities, whichgives in reciprocity with the flow of the electrolyt, which oftencontains turbulances, a considerable noise voltage. A further seriousdifficulty is that, when the electrode will show some form of scale,e.g. because acorn-shells start their formation, the complete electrodesurface is very inhomogeneous and owing thereto the disturbing voltagesbecome larger.

The invention aims at providing an electrode, which e.g. can be used inseawater, in the course of long periods of time, e.g. of the order ofone year, is not subject to changes with respect to the disturbances,and which, moreover, gives the possibility of increasing the exactnessof the measurement considerably, by almost completely eliminating thedisturbances in the voltages indicated in the above.

Accordingly the invention provides a measuring electrode for measuringalternating voltages in a free electrolyt, like seawater, having aconductor adapted to electrically contact the electrolyt, said electrodebeing characterized in that between the conductor and the electrolyt abounded electrolyt body is resent, said body being in free contact withthe conductor and comprising copper ions, and flow limiting means withinsaid body for minimizing liquid exchange between the free electrolyt andthe electrolyt body.

A feature which has proved to be favorable in practice herewith is, thatthe electrolyt body containing copper ions has been separated from thefree electrolyt by means of a perforated wall. Owing to this on the onehand the flow in the free electrolyt passing along the wall is hardlydisturbed and on the other hand a good limitation of the electrolyt bodyis obtained, with which the wall at the same time can serve as amechanical lock in for the flow limiting means.

An embodiment of the invention, which has proved to be favorable inpractice and which can be manufactured simply consists in that theconductor is a thin oblong copper containing wire, which has beenarranged in a regular or irregular configuration in at least part of theelectrolyt body and is surrounded by a manifold perforated insulation.

Another embodiment of the invention, with which also good results havebeen obtained consists in that a structure has been included in theelectrolyt body which contains many fine free passages between theconductor and the free electrolyt.

When applying the invention the conductor preferably consists of copper.By this copper ions in the electrolyt body are obtained whileelectrolytically copper itself has a very constant interfacialpotential.

According to a further improvement of the invention a substance whichincreases the viscosity of a liquid can be added to the electrolyt body,by which the liquid exchange between the electrolyt body and the freeelectrolyt is still further limited.

The invention will now further be elucidated with reference to theaccompanying drawing, in which an embodiment of the invention in sectionhas been shown.

In the drawn embodiment 2 is a recess in a solid body 1. In the recess avery thin copper wire 3, which has been provided with a perforatedinsulation 4, e.g. a thin cotton fabric or a perforated insulatingenvelope, has randomly been folded in the recess 2. The conductor 5 ofthe thread 3 forms the connection of the electrode. The recess 2 isterminated by means of a perforated plate 6 of an electrochemicallyinactive material. Because the wire has been folded to and fro manytimes in a regular or irregular configuration, the movement of theelectrically conducting liquid in the recess 2 is hampered to a veryconsiderable extent. First of all a very strong hampering of themovement takes place at the perforations in the insulation and secondlythe randomly folded wire hampers movements of the liquid in theinterspace between adjacent portions of the wire. Owing to this theliquid in the recess 2 forms a relatively immobilized electrolyt body.

When an electric field occurs in this electrolyt body, the voltage ofwhich field has to be measured by means of a measuring apparatus, thatis connected to the conductor 5 of the wire, the possibility existsthat, e.g. by small inhomogeneities of the conductor 5 at the locationof the thread present in the recess 2, the voltages in e.g. the points 8and 9 do not level with each other. Then also different currentdensities will occur in the points 8 and 9. But since, the electrolytmass in the vicinity of these points is substantially still thedifferences in current density do not cause noise voltages. Moreover,occurring noise voltages, if any, will get smaller and smaller near theplate 6 owing to mutual current exchange and they will amount to nearlyzero at the perforations 7 in the plate 6.

Because the copper of the conductor 5 gradually dissolves in theelectrolyt body inside the recess 2, a relatively high copper ionconcentration will prevail in that recess, said concenlration decreasingsomewhat in the direction of the perforated plate 6. By this high copperion concentration a milieu is maintained in which acorn-shells cannotgrow. Growth of acorn-shells, if any, at the outside of the plate 6, itis true, is counteracted to a considerable less degree, but acorn-shellsformed at that place do not influence the measuring result, as long asthey do not lead to the perforations becoming overgrown. On the otherhand the growth of acorn-shells on a metal surface, which is used as anelectrode, the formation of local extremely thin layers already givesraise to considerable disturbances of the voltage.

With this arrangement one has succeeded in performing measurements withwhich the noise was of the order of magnitude of the Nyquist-noise,which belongs to the space resistance of the electrode. By this thesensitivity of electrodynamic flow velocity meters could be increased toa very considerable degree.

It is pointed out that in the drawn embodiments a structure is formed bythe wire 3 which has been folded to and fro which contains may fine freepassages between the conductor and the free electrolyt. It falls alsowithin the scope of the invention to realize such a structure in otherways.

A substance increasing the viscosity, said substance being known initself, can have been added to the electrolyt in the recess 2. This to afurther degree hampers the movement of the liquid in this recess.

The perforated plate retains the wire 3 within the recess 2, and alsoprovides a uniform restriction on circulation of the electrolyte intoand out of the recess 2, which the perforations 7 assure to electricalcontact with the free electrolyt E.

It is pointed to the fact that the flow limiting means, like the wireand its insulation, do not have a depolarizing function, becausealternating voltages are measured. This can take place in a known waywith flow velocity measurements by exciting the voltages to be measuredwith an alternating magnetic field.

Because the very long conductor 5 of the wire 3 has a large surface inthe recess 2, the interface resistance between this conductor and theelectrolyt body present in the recess 2 is also small which keeps thenoise potential caused by said interface resistance low.

For increasing the double-layer capacity, which is in series with theinterface resistance of the conductor in the electrolyt body, the wirepreferably is carried out in a number of thin parallel sub-wires(Litze).

What I claim is:

l. A system for measuring an electric field in a free electrolytecomprising:

two conductors, at least one of said conductors including an elongatedwire;

means enclosing said elongated wire within a bounded portion of saidelectrolyte and holding said bounded portion of said electrolyte inintimate contact with said elongated wire, said elongated wire beingfolded in multiple strands to and fro within said enclosing means,leaving only small intersticies between adjacent portions of said wirewhich severely impede circulation of said bounded portion of saidelectrolyte; and

means for measuring the voltage drop between said two conductors.

2. The system defined in claim 1, wherein said bounded portion of saidelectrolyte is separated from the free electrolyte by a pervious wall.

3. The'system defined in claim 1, wherein said elongated wire comprisesa plurality of thin copper subwires.

4. A system for measuring an electric field in a free electrolyte,comprising:

two conductors, one of which includes an elongated wire;

means enclosing said elongated wire within a bounded portion of saidelectrolyte and holding said bounded portion of said electrolyte inintimate contact with said elongated wire;

means for a substantially immobilizing circulation of said electrolytein close proximity to said elongated wire, including multiple strands ofsaid wire folded to and fro in said enclosing means; and

means for measuring the voltage drop between said two conductors.

5. The system defined in claim 4, wherein said circulation immobilizingmeans further comprises a viscosity increasing substance added to saidbounded portion of said electrolyte.

6. The system defined in claim 4, wherein said bounded portion of saidelectrolyte is separated from the free electrolyte by a pervious wall;and said elongated wire comprises a plurality of thin copper subwires.

1. A system for measuring an electric field in a free electrolytecomprising: two conductors, at least one of said conductors including anelongated wire; means enclosing said elongated wire within a boundedportion of said electrolyte and holding said bounded portion of saidelectrolyte in intimate contact with said elongated wire, said elongatedwire being folded in multiple strands to and fro within said enclosingmeans, leaving only small intersticies between adjacent portions of saidwire which severely impede circulation of said bounded portion of saidelectrolyte; and means for measuring the voltage drop between said twoconductors.
 2. The system defined in claim 1, wherein said boundedportion of said electrolyte is separated from the free electrolyte by apervious wall.
 3. The system defined in claim 1, wherein said elongatedwire comprises a plurality of thin copper subwires.
 4. A system formeasuring an electric field in a free electrolyte, comprising: twoconductors, one of which includes an elongated wire; means enclosingsaid elongated wire within a bounded portion of said electrolyte andholding said bounded portion of said electrolyte in intimate contactwith said elongated wire; means for a substantially immobilizingcirculation of said electrolyte in close proximity to said elongatedwire, including multiple strands of said wire folded to and fro in saidenclosing means; and means for measuring the voltage drop between saidtwo conductors.
 5. The system defined in claim 4, wherein saidcirculation immobilizing means further comprises a viscosity increasingsubstance added to said bounded portion of said electrolyte.
 6. Thesystem defined in claim 4, wherein said bounded portion of saidelectrolyte is separated from the free electrolyte by a pervious wall;and said elongated wire comprises a plurality of thin copper subwires.